The present invention relates to the field of communications, and more particularly, to phased array antennas.
Existing microwave antennas include a wide variety of configurations for various applications, such as satellite reception, remote broadcasting, or military communication. The desirable characteristics of low cost, light-weight, low profile and mass producibility are provided in general by printed circuit antennas wherein flat conductive elements are spaced from a single essentially continuous ground element by a dielectric sheet of uniform thickness. The antennas are designed in an array and may be used for communication systems such as identification of friend/foe (IFF) systems, personal communication service (PCS) systems, satellite communication systems, and aerospace systems, which require such characteristics as low cost, light weight, low profile, and a low sidelobe.
The bandwidth and directivity capabilities of such antennas, however, can be limiting for certain applications such as space applications. Furthermore, while a microstrip patch antenna is advantageous in applications requiring a conformal configuration, e.g. in aerospace systems, mounting the antenna presents challenges with respect to the manner in which it is fed such that conformality and satisfactory radiation coverage and directivity are maintained and losses to surrounding surfaces are reduced.
More specifically, increasing the bandwith of a phased array antenna with a wide scan angle is conventionally achieved by dividing the frequency range into multiple bands. This approach results in a considerable increase in the size and weight of the antenna while creating a Radio Frequency (RF) interface problem. Also, gimbals have been used to mechanically obtain the required scan angle. Again, this approach increases the size and weight of the antenna, and results in a slower response time.
Additionally, prior art phased array antennas often have an antenna feed structure including coaxial feed lines to be connected to the various antenna elements. These coaxial feed lines are typically parallel to a common axis and soldered together to form the antenna feed structure. The feed structure is inserted through the antenna""s substrate for connection with the antenna elements. Yet, it may be difficult to properly ground such antenna feed structures while connecting them to the antenna elements, which may result in undesirable common mode currents, for example.
Thus, there is a need for a lightweight patch dipole phased array antenna with a wide frequency bandwith and a wide scan angle, and that can be conformally mountable to a surface.
In view of the foregoing background, it is therefore an object of the invention to provide a lightweight patch dipole phased array antenna with a wide frequency bandwith and a wide scan angle, and that can be conformally mountable to a surface.
This and other objects, features and advantages in accordance with the present invention are provided by an antenna including a substrate including a ground plane and a dielectric layer adjacent thereto and at least one antenna unit carried by the substrate. The at least one antenna unit may include a plurality of adjacent antenna elements arranged in spaced apart relation from one another about a central feed position on the dielectric layer opposite the ground plane. The at least one antenna unit may also include an antenna feed structure including a respective coaxial feed line for each antenna element and a feed line organizer body having passageways therein for receiving respective coaxial feed lines.
More specifically, the feed line organizer body may include a base connected to the ground plane and a guide portion carried by the base. The base and the guide portion may be integrally formed as a monolithic unit, for example. Moreover, the guide portion may include a bottom enclosed guide portion carried by the base, a top enclosed guide portion adjacent the antenna elements, and an intermediate open guide portion extending between the bottom enclosed guide portion and the top enclosed guide portion adjacent the antenna elements. Each coaxial feed line may be soldered to the feed line organizer body at the intermediate open guide portion. Furthermore, the antenna feed structure may include a tuning plate carried by the guide portion. Additionally, the passageways may each be parallel to a common axis, and the feed line organizer may include at least one conductive material, such as brass, for example.
The ground plane may extend laterally outwardly beyond a periphery of the at least one antenna unit. Also, the antenna may further include at least one hybrid circuit carried by the substrate and connected to the antenna feed structure. Each antenna element may have a generally rectangular shape, and the at least one antenna unit may include a plurality of antenna units arranged in an array. Furthermore, the dielectric layer may have a thickness in a range of about xc2xd an operating wavelength of the at least one antenna unit. Additionally, there may be at least one impedance matching dielectric layer on the at least one antenna unit.
A method aspect of the invention is for making an antenna and includes providing at least one antenna unit on a substrate comprising a ground plane and a dielectric layer adjacent thereto. The at least one antenna unit may include a plurality of adjacent antenna elements arranged in spaced apart relation from one another about a central feed position on the dielectric layer opposite the ground plane. Additionally, the substrate may have an opening therein exposing portions of the plurality of adjacent antenna elements. The method may further include forming an antenna feed structure by positioning respective coaxial feed lines within passageways of a feed line organizer body. Further, the antenna feed structure is inserted into the opening, and each of the coaxial feed lines is connected to a respective antenna element.